If you have vertigo or acrophobia, you will have trouble with “The Walk,” the story of Frenchman Philippe Petit’s tightrope walk between the towers of the World Trade Center. If you don’t have vertigo or acrophobia, you might have after you watch the movie, with the most stunningly realistic 3D effects ever put on screen. At least I think they’re still just on the screen. It sure feels like it goes on way, way behind it.

“Man on Wire,” a documentary about Petit’s 1974 stunt, or, as he might prefer to say, coup, won an Oscar in 2008. In this film, Joseph Gordon-Levitt, with an accent that just manages to avoid Pepe LePew dimensions, plays Petit, a street performer who saw a photograph of the World Trade Center in the waiting room of his dentist and was instantly consumed with the dream of a walk in the sky, more than 1300 feet above the sidewalk, between the towers. Like Petit himself, the movie does not bother with the question of why this might be a good thing to do. If pressed, he might just say, like Mallory, “Because it’s there.” The problem is that he doesn’t have an answer but still keeps talking and talking. For no reason we keep going back to Petit narrating the story from the torch of the Statue of Liberty. It is distracting and dull.

Petit could not or would not articulate it, but I think I know why. When huge institutions get together to create a world-record setting edifice — taller than the Eiffel Tower, the Frenchman notes — there is something irresistibly enticing about coming back as a lone soul and literally topping it. Director Robert Zemeckis, who can get more excited about the technology than the story in his films, may identify with that challenge. Petit wanted to walk across the sky, with an audience to appreciate it. And Zemeckis wants to recreate that experience for us, taking us to the roof of the Towers, and inviting us to look down.

Still, while we love movies about dreamers of impossible dreams who make them come true, we do like to have a reason, and Petit edges over the line from audacious dreamer to inconsiderate narcissist, despite Gordon-Levitt’s considerable appeal. This lends a hollow quality, overcome less from the story of the film to what is in our own hearts as we watch, knowing what the tragedy that lies ahead for the World Trade Center.

What works well in the first part of the film is Petit’s tutorials with a tightrope master played by Sir Ben Kingsley and the procedural elements once Petit and his team get to New York and start preparing as though they are getting ready to rob a bank. Indeed, it becomes a heist film of a sort because they have to find different ways to sneak into a building that is still under construction and gather the information they need to figure out how to install the cable and keep it from swaying or buckling. And then to install it. There are a lot of problems along the way, including Petit stepping on a nail and injuring his foot and dropping his black turtleneck from the roof when he is trying to assume his performer persona. They omit, however, my favorite detail from the documentary: Petit explains that in America, if there’s pencil in your pocket everyone assumes you are part of the construction team and are entitled to be there. Like the loss of the buildings themselves, Petit’s ability to exploit lax security is a poignant reminder of what we no longer have.

The last half hour or so of the film is breathtaking and well worth the price of admission in IMAX 3D. You will feel that you are on the tightrope with Petit. As the crowd gathers below and the police arrive (who thought a police helicopter would be a good idea?), Petit is suspended in the clouds, mentally, emotionally, and physically. For just a moment, Zemeckis and Gordon-Levitt bring us up there with him, and his dream, however frivolous and ephemeral, becomes ours.

Parents should know that this film has very risky and dangerous behavior, vertiginous 3D effects, brief nudity, some strong language, and smoking and drinking.

Family discussion: What big dream would you like to make come true? Who would you want to be your team?

If you like this, try: the documentary “Man on Wire”